The present invention relates to a method for estimating the portion of undesired particles in crop material.
The quality, in particular the purity of a crop material such as grain, is a decisive factor in determining the type of further processing to carry out, and is therefore also a decisive factor for the price that the farmer may obtain for the crop material. The purchaser of the crop material generally defines limiting values for the portion of undesired particles in the crop material, that is, the purchase price drops if the portion of undesired particles in the crop material exceeds these limiting values.
The manner in which the crop material is harvested has a substantial effect on the quantity of undesired components contained therein. With a combine harvester, for instance, when the threshing mechanism setting is too acute, a high percentage of damaged grain results, which is undesired, because this has a negative effect on the durability of the grain. If the setting is too gentle, grains that have not been fully threshed enter the crop material, and this interferes with the further processing of the grain. Husks and short straw that enter the crop-material flow during threshing may indeed be removed in a wind separator located downstream of a threshing stage, although a setting of the wind separator that is too acute may also result in grain losses. It is therefore very important to the farmer that it be possible to reliably meet the requirements he set in terms of the quality of the crop material, but also to avoid crop-material losses that are not required to remain within the specified level of quality.
It is therefore desirable to be able to evaluate the quality of the crop material during the harvesting process itself, in order to implement measures required to attain the level of quality required, or to avoid unnecessary losses.
Publication EP 1 763 988 A1 makes known a method for adjusting a working unit of a harvesting machine, with which photographs are taken of a crop-material flow. An operator of the harvesting machine may use these photographs, in particular by comparing them with stored reference photographs, to evaluate the level of contamination of the crop material and to change the operating parameters of the harvesting machine if necessary, in order to improve the quality of the crop material or to reduce crop-material losses.
The conventional method that the operator of the machine uses to evaluate the crop-material quality is not entirely objective, however, and the efficacy of the method depends greatly on the amount of attention that the operator is able to devote to managing the crop-material quality. This amount of attention is generally not very high, since the operator is simultaneously occupied with controlling the harvesting machine.
DE 197 20 121 C2 discloses a method for performing a quantitative determination of undesired components such as leaves and dirt in sugar beets or spoiled pieces of fruit among harvested wine grapes, with which color photographs are taken of the crop material, color histograms of these photographs are created, and the portion of undesired components in the crop material is deduced based on the portion of color values in the histograms that are assigned to the undesired components. In order to deliver reliable results, a method of this type requires that the color differences between desired and undesired portions of the crop material be distinct.
Since the method is incapable of distinguishing between the image of an unattached, well-illuminated but dark object and an image of an object that is light per se but that is located in the shadow of other objects, a measurement performed using this method unavoidably contains a significant background signal. This is acceptable when the method is used by the purchaser of the crop material, since, in order to evaluate the price to be paid, the operator need only verify that the specified limiting values for the purity of the crop material have been met, and he does not have to determine the extent to which they may have been fallen below.
This is what makes the method made known in DE 197 20 121 C2 essentially unusable for the producer of the crop material.